The field of automotive emission controls represents an area which is receiving a great deal of attention, particularly as government regulations concerning automotive pollution become more and more strict. It is now accepted that some sort of catalytic control system will be necessary in order that automobiles may meet future regulations, particularly with regard to emissions of oxides of nitrogen.
Potential catalysts must be evaluated from at least three view points; effectiveness, durability and cost. The catalysts systems proposed in the past have been deficient in one or more of the factors. Noble metal catalysts such as platinum or rhodium are effective and may be long lasting but they are extremely expensive while non-noble metal catalysts such as certain nickel base, stainless steel, and copper base alloys have not shown themselves to be durable enough for commercial use.